The invention relates to an injection device, having a needle and having an armature which is connected to the needle such that a movement of the needle can be generated by way of a movement of the armature, wherein the armature has at least one passage bore through which fuel can be conducted to a needle tip.
For the operation of internal combustion engines, fuel and air is mixed and ignited, wherein the energy stored in the fuel is converted into mechanical work and then utilized for the propulsion of a motor vehicle. To supply the fuel to the air, use is made of injection units which are arranged either in the intake tract or in the combustion chamber of the internal combustion engine. In this regard, mechanical injection devices, piezoelectric injectors and coil-type injectors are known from the prior art. In this case, there is arranged in the interior of an injector housing a needle by means of which outlet openings provided in a housing can be opened and closed. In general, the needle moves in a linear direction of movement from an open position into a closed position and vice versa, such that in the open state, the fuel can flow through the outlet openings and is admixed to the air.
Such systems however have the disadvantage that, in the closed state of the injection device, the needle comes to lie on the housing at the same location. Contaminants, for example particles, entrained in the fuel are in this case forced against the internal wall of the housing by the needle. Said contaminants thus accumulate on the sealing surface between needle and housing and lead to leakages of the injection device. As a result, fuel can continue to pass through the outlet openings even when the needle is in the closed state. This disrupts the normal operation of the engine and leads to increased fuel consumption of the vehicle.
It is the object of the present invention to specify an injection device which overcomes the disadvantages presented in the prior art. In particular, it is an object of the invention to specify an injection device which exhibits high reliability and functional dependability and with which a high level of leak-tightness of the system is simultaneously realized.
Said object is achieved by means of a device having the features of the independent claim. The dependent claims relate to advantageous embodiments of the invention.
To achieve said object, the invention proposes an injection device for an internal combustion engine, having a needle, wherein the armature is operatively connected to the needle such that a movement of the needle can be generated by way of a movement of the armature, wherein the armature has at least one passage bore through which fuel can be conducted to a needle tip. Furthermore, the injection device may be characterized in that a longitudinal axis of the needle and a longitudinal axis of the passage bore are in a skewed orientation relative to one another. By means of this oblique orientation of the passage bore through the armature, the throughflow of fuel subjects the armature to a torque which acts about the longitudinal axis of the needle. Said torque is transmitted by friction to the needle, whereby a rotational movement of the needle is generated. During the closing process, the rotational momentum of the needle has the effect that contaminants are constantly rubbed away from the sealing surface.
Furthermore, the passage bore may comprise an inlet opening and an outlet opening in the armature, wherein the distance between the inlet opening and the longitudinal axis of the needle is smaller than the distance between the outlet opening and the longitudinal axis of the needle. In this way, the longitudinal axis of the passage bore lies in a plane which is oriented parallel to the longitudinal axis of the needle and which encloses an acute angle with a tangential plane of a circular path running around the longitudinal axis of the needle. Owing to the orientation of the passage bore, it is possible for rotational momentum to be imparted to the armature as the injection device opens, that is to say at the moment when the needle opens up the outlet opening of the injection device.
Furthermore, the armature may be arranged rotatably on the needle.
Furthermore, the armature may be arranged so as to be rotatable about the needle, wherein the needle is provided in a centrally arranged bore of the armature. This positioning of the needle in the armature yields a symmetrical overall construction, whereby particularly uniform and reproducible rotational movements of the armature, and thus also of the needle, can be generated.
In a preferred embodiment of the invention, the injection device is in the form of a coil-type injector.
Furthermore, the armature may have a multiplicity of passage bores, the inlet openings and outlet openings of which are arranged radially on a circular path around a longitudinal axis of the needle situated centrally in the armature, wherein the longitudinal axis of the passage bore encloses an acute angle with a tangential plane of the circular path. Through the provision of multiple passage bores, it is possible to realize a particularly good rotational movement of the armature, and thus of the needle, which can be repeated upon every injection process.
The angle between the tangential plane of the circular path and the longitudinal axis of the passage bore may lie in the range of +45° to −45°, preferably in the range of +30° to −30° and particularly preferably in the range of +15° to −15°. In this range, the fuel jet emerges from the passage bore and imparts an ideal action to the armature such that an optimum rotational movement of the armature about the longitudinal axis of the needle is generated.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.